Hydraulic impulse tool with enhanced fluid seal

Abstract

An impulse tool (10) including an impulse generator (19, 119) utilizes an enhanced seal to reduce leakage of hydraulic fluid. The annular clearance in the pressure plate (24, 124) is sealed around the spindle (30, 130) with a resilient seal (38, 138). A primary passage (40, 140) through the pressure plate is provided to compensate for expansion of the fluid. The use of the primary passage (40, 140), which is not susceptible to enlargement due to wear, minimizes pressure peaks in the accumulator reservoir (42, 142), and results in less leakage.

What is claimed is: 
     
       1. An impulse unit, comprising: a rotary torque impulse generator including a fluid chamber, the fluid chamber comprising: a base cap,   a cage coupled to the base cap, and   a pressure plate formed with an aperture therethrough and coupled to the cage;     a spindle having one or more impulse receiving pulse blades extending into the fluid chamber through the aperture in the pressure plate;   a resilient seal mounted on the pressure plate adjacent the aperture, for preventing transmission of transient pressure peaks outside the fluid chamber and preventing leakage of fluid through the aperture for the spindle in the pressure plate;   an accumulator reservoir defined outside of the fluid chamber operable to allow volumetric expansion of the fluid and to replenish lost oil due to leakage;   the pressure plate formed with a primary restrictive passage therethrough, the primary restrictive passage located in and extending through the pressure plate remote from the aperture for the spindle and communicating on one side thereof with the fluid chamber and on the other side thereof with the accumulator reservoir, the primary passage operable to minimize pressure peaks within the accumulator reservoir; and   an accumulator piston partly defining the accumulator reservoir, forming a boundary between the accumulator reservoir on one side and the atmosphere on the other, the piston operable to adjust the volume of the accumulator reservoir in relation to occurring volume changes in the hydraulic fluid during operation of the impulse unit.   
     
     
       2. The impulse unit of claim 1, wherein the accumulator reservoir comprises: an end cap which concentrically surrounds the spindle; and   the accumulator piston, which is movably guided in the end cap.   
     
     
       3. The impulse unit of claim 2, wherein the accumulator piston further comprises at least one outer seal ring at its outer periphery for cooperation with the end cap and at least one inner seal ring at its inner periphery for cooperation with the spindle to substantially seal off any fluid flow therebetween. 
     
     
       4. The impulse unit of claim 2, further comprising a biasing means for urging the accumulator piston toward the pressure plate to compensate for decreasing volume in the accumulator reservoir. 
     
     
       5. The impulse unit of claim 1, further comprising a spring means for biasing the annular accumulator piston toward the pressure plate. 
     
     
       6. The impulse unit of claim 5, wherein the spring means comprises an elastomeric spring. 
     
     
       7. The impulse unit of claim 5, wherein the spring means comprises a coiled flat wire spring. 
     
     
       8. The impulse unit of claim 1, further comprising: a recessed slot in the pressure plate;   a secondary restrictive passage operable to dissipate pressure peaks during reverse operation; and   the secondary restrictive passage communicating on one side thereof with the primary restrictive passage and on the other side thereof with the recessed slot in the pressure plate.   
     
     
       9. The impulse unit of claim 8, wherein the recessed slot further comprises a kidney-shaped configuration. 
     
     
       10. A rotary torque tool having an impulse unit and a motor, comprising: a fluid chamber having a pressure plate;   a motor;   a drive member coupled to the motor;   a spindle having one or more impulse receiving pulse blades extending into the fluid chamber through an aperture in the pressure plate, a portion of the spindle associated with the drive member;   fluid retaining means associated with a portion of the spindle and arranged to divide the fluid chamber into at least one high-pressure compartment and at least one low-pressure compartment during a limited portion of a relative rotation between the drive member and the pulse spindle, thereby producing transient port impulse generating pressure peaks in the at least one high pressure compartment;   a resilient seal mounted on the pressure plate adjacent the spindle for preventing transmission of transient pressure peaks outside the fluid chamber and preventing leakage of fluid through the aperture for the spindle in the pressure plate;   an accumulator reservoir defined outside of the fluid chamber operable to allow volumetric expansion of the fluid and to replenish lost oil due to leakage;   a primary restrictive passage operable to minimize pressure peaks within the accumulator reservoir, the primary restrictive passage located in and extending through the pressure plate remote from the aperture for the spindle and communicating on one side thereof with the fluid chamber and on the other side thereof with the accumulator reservoir; and   an accumulator piston partly defining the accumulator reservoir, forming a boundary between the accumulator reservoir on one side and the atmosphere on the other, the piston operable to adjust the volume of the accumulator reservoir in relation to occurring volume changes in the hydraulic fluid during operation of the impulse unit.   
     
     
       11. A method for manufacturing an impulse unit comprising the steps of: forming a fluid chamber that includes a base cap, a cage coupled to the base cap, and a pressure plate with a spindle-receiving aperture formed therethrough;   disposing a spindle within the fluid chamber such that a portion of the spindle extends through the aperture in the pressure plate and the portion of the spindle is coupled to the base cap of the fluid chamber;   coupling an impulse generator to the spindle within the fluid chamber;   placing a resilient seal on the pressure plate adjacent the spindle to form a substantially leakproof seal between the spindle and the pressure plate;   forming an accumulator reservoir with a pressure regulating means; and   forming a primary passageway through the pressure plate to place the fluid chamber in restricted fluid communication with the accumulator reservoir to minimize pressure peaks being transmitted from the fluid chamber to the accumulator reservoir while allowing adjustment of the fluid in response to volumetric changes.   
     
     
       12. The method of claim 11 wherein the step of forming a primary passage comprises the steps of: drilling a hole substantially through the pressure plate with a first diameter;   punching a second hole with a second diameter in the pressure plate connecting one side of the pressure plate with the first hole, the second diameter sized less than the first diameter of the first hole.   
     
     
       13. The method of claim 11 wherein the step forming an accumulator reservoir with a pressure regulating means further comprises the step of forming one portion of the accumulator reservoir to have a biasing surface responsive to volume decreases to thereby hold a substantially consistent pressure in the accumulator reservoir.